High voltage electron discharge diode



Sept. 28, 1965 o. H. SCHADE, SR 3,209,195

HIGH VOLTAGE ELECTRON DISCHARGE DIODE Filed March 13, 1961 2Sheets-Sheet l made! 3 w Mada/7a Z'Z' 07m 16 50/424 61?.

S pt 8, 1965 o. H. SCHADE, SR

HIGH VOLTAGE ELECTRON DISCHARGE DIODE 2 Sheets-Sheet 2 Filed March 13,1961 United States Patent 3,209,195 HIGH VOLTAGE ELECTRON DISCHARGEDIODE Otto H. Schade, Sn, West Caldwell, N.J., assignor to RadioCorporation of America, a Corporation of Delaware Filed Mar. 13, '1961,Ser. No. 95,129 13 'Claims. (CL 313-246) This invention relates toelectron discharge devices and more particularly to electron tubes ofthe high voltage rectifier type.

During the normal operation of a rectifier tube the anode thereof isalternately driven positive and negative with respect to the cathode. Incertain rectifier tube applications, such as in color televisionreceivers, the difference in potential between the rectifier anode andcathode may be as much as 30,000 volts. These potential differencesproduce harmful electrostatic field densities and forces within thetube, which, as well known, limit the magnitude of voltages which may beapplied to the rectifier tube electrodes, thereby limiting the possibleutility of the tube.

Thus, for example, if during the inverse voltage peak, that is, when theanode of the rectifier is negative with respect to the cathode, theelectrostatic field density or potential gradient at the surface of theanode should reach a value of the order of 100,000 volts per centimeter,cold or field emission takes place. Electrons are pulled from the anodeand are accelerated toward the cathode and metal cathode supports. Someof the electrons miss the metal supports and bombard the tube envelope,causing eventual rupture of the envelope and failure of the tube.Moreover, since cold emission of electrons from the anode surfaceusually occurs from small areas of the anode, the electron current beingfocussed onto still smaller areas of the cathode structure or envelope,the result of such cold emission is often localized heating of the tubecom ponents and the formation of hot spots thereon. Such hot spotsresult in the evolution of gases, the gases being detrimental to theoperation of the cathode.

The eifects of electrostatic forces Within the tube are that mechanicalstress-es are exerted thereby on the electrodes which may also beharmful to the operation of the tube. At each negative swing of theanode potential with respect to the cathode, for example, anelectrostatic force is created which tends to pull the electron emittingcathode coating from the cathode. This electrostatic force isproportional to the square of the potential gradient at the surface ofthe cathode, and excessive cathode surface gradients may result in atearing or peeling off of coating from the cathode and a disruption ofthe electron emission therefrom.

As known, the potential gradients within an electron tube for givenelectrode potentials are determined by the spacings between the tubeelectrodes and upon the smoothness and radius of curvature of the tubecomponents. Small electrode spacings and tube components having sharpedges or rough surfaces tend to produce high potential gradients. Priorart practice, accordingly, has been to fabricate rectifier tubes havinglarge dimensions in order to provide large electrode spacings, toprovide electrodes and other tube components having polished surfaces,and to provide gradient shields having large radii of curvature forelectrostatically shielding tube components having sharp edges or roughsurfaces from the other tube electrodes. Such prior art practices haveresulted in rectifier electron tubes which are expensive, and which areof undesirably large size.

Accordingly, it is an object of this invention to provide an improvedrectifier electron tube which is economical of manufacture and which hasunusually large voltage handling capabilities with respect to its size.

3,209,195 Patented Sept. 28, 1965 A still further problem caused by highpotential gradients is flash-over or break-down of the air surroundingthe tube envelope. Tube flash-over is somewhat equivalent to a directshort circuiting of the tube electrodes and can result in destruction ofthe tube or the electronic equipment utilizing the tube. It is knownthat flash-over may occur even though a large insulating member isprovided between the tube electrodes. That is, in some prior art tubes,the location of the tube electrodes and gradient shields with respect tothe insulating member is such that the potential distribution along theinsulating member separating the tube electrodes is non-linear, most ofthe change in potential between the electrodes occurring over only ashort length of the insulating member. The result of this is that highvoltage gradients are thus produced along these short lengths whichoften lead to localized break-down of the surrounding air and failure ofthe electronic equipment.

Therefore, a further object of this invention is to provide an improvedrectifier tube wherein the formation of excessively large potentialgradients along the insulation between the tube electrodes is avoided.

More particularly, it is an object of this invention to provide arectifier tube of improved construction in which relative dimensions ofthe tube parts result in the avoidance of the formation of undesirablylarge potential gradients.

For achieving these and other objects in accordance with this invention,an electron tube is provided which comprises an envelope including acup-shaped header assembly, a tubular ceramic insulator, and acup-shaped anode. The envelope parts referred to are secured together instacked end-to-end relationship, the ceramic insulator separating theanode from the header assembly, and the latter two parts closingopposite ends of the envelope.

The cup-shaped header assembly comprises a conductive tubular portionhaving one end secured to the ceramic insulator and its other end closedby a ceramic closure member or wafer. Mounted within the header assemblyand conductively secured to the tubular portion by an annular, disk-likemember is an elongated tubular conductive cathode support. The cathodesupport extends axially of the ceramic insulator and into the anode, andhas a cathode assembly including either a filamentary cathode or anindirectly heated cathode electrically connected with and supported onthe end thereof within the anode. Included within the cathode supportbut electrically insulated therefrom is a conductor, one end of theconductor extending into the anode for supporting and making electricalcontact to the cathode, the other end of the conductor being secured toa lead-in extending through the ceramic closure wafe. The lead-in andthe header assembly tubular portion serve as the terminals for thecathode, the anode envelope portion serving as the anode terminal.

As will be described in detail hereinafter, advantages .of thisconstruction are that the tube parts may be easily assembled and securedtogether, the electrode supports are tubular or circular having roundedand smooth surfaces for avoiding the formation of excessively highgradients, and certain portions of the electrode supports are utilizedas gradient shields for certain other portions of the electrodesupports.

Moreover, as will also be described hereinafter, the dimensions of thevarious tube parts are carefully chosen with respect to each other forreducing the formation of high potential gradients at the anode andcathode surfaces, and along the ceramic insulator.

In the drawing:

FIG. 1 is a longitudinal section, partially broken away, showing anelectron tube according to this invention;

FIG. 2 is a view along line 2-2 of FIG. 1;

FIG. 3 is a partial section of a modification of the device shown inFIG. 1;

FIG. 4 is a vertical section of another modification of the device shownin FIG. 1;

FIG. 5 is a graph showing the relationship between potential gradientswithin an electron tube having coaxial tubular electrodes and the ratioof diameters of the tube electrodes;

FIGS. 6a, b and c illustrate the effect of tube geometry on potentialdistribution along the insulating member; and,

FIGS. 7 and 8 are longitudinal sections showing a brazing jig and anexhaust jig, respectively, of the types which may be employed in thefabrication of tubes made according to this invention.

As shown in FIG. 1, one embodiment of a rectifier electron tube madeaccording to this invention comprises a .metal and ceramic envelope 10including a cup-shaped metallic anode 12, a tubular ceramic insulator 13and a cup-shaped header assembly 14. Header assembly 14, in turn,comprises a conductive metallic tubular portion 16 and a ceramic closuremember 18. The ceramic wafer 18 is secured within a longitudinallyextending flange 19 at the periphery of one end 20 of tubular portion16, the other end 21 of tubular portion 16 being secured to ceramicinsulator 13.

Axially disposed within envelope 10 is a cathode mount 24 including anelongated tubular conductor 26 mounted at one end 27 thereof to anannular flange member 29. Flange 29 has a centrally disposed tubular orcup-like portion 30 for receiving the end 27 of tubular conductor 26,and has a peripheral downwardly turned lip for engaging and securing theflange 29 with tubular portion 16 of header assembly 14. Included withintubular conductor 26 and extending axially and outwardly of each endthereof is a conductor rod 31. Conductor rod 31 is secured at its lowerend 32 within the tubular portion 33 of an annular flange member 34mounted on conductive lead-ins 36 extending through the ceramic wafer18. The upper end 38 of conductor rod 31 is secured within tubularconductor 26 by an insulator washer 40'. Swage or flare 41 on conductorrod 31 maintains washer 40 in place, conductor rod 31 nowhere touchingthe inner walls of tubular conductor 26, being electrically insulatedtherefrom.

Tubular conductor 26 extends axially of ceramic insulator 13 into anode12, and has mounted at the top end 43 thereof within the anode 12 acathode filament support structure 45. As shown in FIGS. 1 and 2,filamerit support 45 comprises two U-shaped conductive rods 46 arrangedto form a basket-like structure. The ends of rods 46 are formed inwardlyand are secured within the top end 43 of the tubular conductor 26. Sincethe number of rods 46 and the diameter of the basket-like filamentsupport 45 affect the potential gradients within the rectifier tube, aswill be described hereinafter, one, two, or more rods forming supportstructures of varied diameters may be used depending upon the amount offilament shielding desired.

Mounted within filament support 45 is a cathode filament 48. One end offilament 48 is secured to and suspended from the inside top end 49 offilament support 45 and the other end thereof is secured to the top end38 of conductor rod 31. The complete electrical circuit for the cathodefilament 48 comprises lead-ins 36, which serve as one terminal forfilament 48, annular flange 34, conductor rod 31, the cathode filament48, the filament support 45, tubular conductor 26, flange 29, and headerassembly tubular portion 16. Tubular portion 16 serves as the otherterminal for filament 48.

As shown in FIG. 3, an alternative construction of the tube shown inFIG. 1 employs an indirectly heated cathode 52 comprising a cathodesupport sleeve 53 mounted on the end 43 of tubular conductor 26, and acathode cup 54 mounted on sleeve 53. Cathode cup 54 has an electronemissive material 55 coated thereon. Included within sleeve 53 is aheating element 56 in the form of a helical coil, one end of the coilbeing secured within cathode sleeve 53 and the other end thereof beingsecured to conductor rod 31, as by welding. Aluminum oxide insulatingmaterial 57 is provided on the heating coil 56 and the end of conductorrod 31 for insulating the turns of the heating element 56 from eachother and from the cathode sleeve 53 and for insulating conductor rod 31from the inner walls of cathode support 26. Since aluminum oxide has acertain degree of structural strength, a sufficient quantity of it isused for insulatingly supporting conductor rod 31 within cathode support26, thereby eliminating the need for insulating washer 40 used in theembodiment of FIG. 1. Also, the tube portion shown in FIG. 3 is part ofa tube having a lower end similar to that of the tube shown in FIG. 1.For the tube of FIG. 3, however, lead-ins 36 serve as one terminal forthe heating element 56, while header assembly tubular portion 16 servesas the terminal for both cathode 52 and the other end of heating element56, the latter being electrically secured to cathode 52, as described.

Having thus described an embodiment of this invention, certainadvantages and features thereof will now be discussed.

In FIG. 5 is shown a graph illustrating the relationship between themagnitude of potential gradients within a coaXial tubular electrodeelectron tube and the ratios of electrode diameters. The ordinate of thegraph indicates potential gradients in kilovolts per centimeter, and theabscissa indicates the ratio of cathode to anode diameters for a tubularelectrode structure. Curve 2 indicates the potential gradient at thesurface of the anode, and curve 1 the gradient at the surface of thecathode. For the purpose of illustration, the diameter of the anode istwo centimeters, and the potential differential between anode andcathode is one thousand volts. For the computation of the cathode toanode diameter ratios, the diameter of the largest element of thecathode assembly within the anode electrode at cathode potential istaken as the cathode diameter. This is because the largest diameterelement determines the maximum anode surface gradient, and to a largedegree, as will be discussed hereinafter, the maximum cathode surfacegradient. In this embodiment the value of cathode assembly diameter isthe outer diameter of filament support 45 for the tube constructionshown in FIG. 1 or the diameter of cathode cup 54 for the constructionof FIG. 3. For tubular electrode structures having other values of anodediameters and potential differentials, the shape of the curves shown inFIG. 5 is unaffected, the actual values of potential gradients beingcalculable by use of suitable multiplying factors.

It is apparent from these graphs that low electrode diameter ratiosproduce small gradients at the anode surface (curve 2), while smalldiameter ratios produce large gradients at the cathode surface (curve1). The applicant has discovered, however, that the effects of largepotential gradients at the anode surface are more likely to causedisruption of tube performance than are large gradients at the cathodesurface. Moreover, because the rate of reduction in potential gradientsat the cathode surface with increasing diameter ratios is very rapid atlow diameter ratios while the rate of cathode surface gradientimprovement with increasing diameter ratios is much smaller at higherratios, the applicant, has determined that practical upper and lowerlimits for the diameter ratios are in the order of 0.2 and 0.09, respec:tively. At the lower limit, the anode surface gradinet is small whilethe cathode surface gradient is not excessively high. At the upperlimit, the anode surface gradient has not yet become too high, whereasfurther in-' creases in diameter ratios have little effect towardsimproving the cathode surface gradients.

In the drawings of FIG. 6a, b and c, the effect of the ratio of tubularconductor 26 diameter to ceramic insulator 1 3 diameter upon thelinearity of the potential distribution along ceramic insulator '13 isshown. The numbered dash lines 60 of these drawings are equipotentiallines, the electrostatic field being normallized such that the anodepotential is at a potential of 1.0 volts and the cathode assembly,tubular conductor 26 and flange 29 are at zero volts potential. Thespacing of the equipotential lines 60 indicate the magnitude of thepotential gradients at and near the lines, the closer the spacingsbetween lines 60, the greater the potential gradients.

In FIG. 6a the ratio of tubular conductor 26 outer diameter to theceramic insulator 13 inner diameter is 0.5, in FIG. 6b, 0.2; and in FIG.60, 0; tubular conductor 26 being assumed to have an infinitestimaldiameter in the latter figure for the purpose of illustration. As shown,the smaller the diameter ratio, the more uniform are the spacingsbetween the equipotential lines 60. For a fixed length of ceramicinsulator 13, the smallest value of the maximum potential gradient alongceramic insulator 1-3 occures when the spacings between equipotentiallines 60 are preferably equal, that is, when the diameter -of tubularconductor 26 is infinitesimal.

For providing adequate strength to tu'bular conductor 26 for supportingitself and the cathode mounted therein, tubular conductor 26 must have adiameter greater than some minimum value. Since the tubular conductor isat cathode potential and extends into anode 12, the upper diameterlimits imposed upon the cathode assembly within the anode, as described,also apply to tubular conductor 26. The maximum diameter of the tubularconductor, or at least that portion of it within anode 12, therefore,should be no greater than the diameter of the cathode 52 or filamentsupport 45. Since the diameter of ceramic insulator '13 may be less thanthe diameter of anode 12, as shown in FIG. 3, however, the applicant hasdetermined that the largest diameter of tubular conductor 26 withinceramic insulator 16 for preventing excessively high gradients along theceramic insulator should be less than 0.2 of the inner diameter of theceramic insulator. Likewise, the minimum diameter of the portion oftubular conductor 26 within ano'de 12 should be no less than 0.09 of theinner diameter of the anode. Within ceramic insulator 16, the tubularconductor diameter should be as small as possible consistent with themechanical strength requirements of the tubular conductor and conductorrod 31 therein.

A feature of the invention is that the electrodes and electrode supportsof the rectifier tube either have rounded and smooth surfaces or elseare electrostatically shielded for preventing formation of highpotential gradients.

The tubular anode 12, tubular ceramic insulator '13, and the tubularportion 16 of the header assembly 14 are all provided with smoothsurfaces having large radii of curvature. Within header assembly 14(FIG. 1) annular flange 29 represents a large, smooth surface towardsthe anode end of the tube and serves as a gradient shield for the end 27of tubular conductor 26, the end 32 of conductor rod 31, and lead-ins'36 extending through closure wafer 18. For preventing the formation ofa large potential gradient at the joint 15 between anode 12 and ceramicinsulator 13, the inner edge 61 of the insulator is beveled as shown inFIG. 1. An alternate arrangement, as shown in FIG. 3, is to provide agradient shield 62 secured to anode =12, shield 62 extending downwardlypast the anode-insulator joint 15 to electrostatically shield the jointfrom the cathode. A still further alternative, as shown in FIG. 4,comprises a ceramic ring 68 which is provided between the ends of theceramic insulator 1'3 and the anode 12. The ring 68 is brazed to theseparts by a suitable brazing material by suitable known techniques. Uponheating and flow of brazing material to provide the brazed joints, themolten brazing material flows over and coats the entire ring 68 with asmooth metallized surface. This surface along with the curved insidesurface 69 of the ring 68 avoids excessive gradients at theanode-ceramic insulator joint.

The cathode assembly is also designed to present the smoothest possiblesurface towards the anode for avoiding excessively large gradients.Extrusion or drawing methods are employed to fabricate cathode sleeve 53and cup 54 (FIG. 3), whereby these elements as provided are seamless andcompletely smooth surfaced. The heating element 56 and the upper end 38of conductor rod 31 are wholly contained within sleeve 53, thereby beingcompletely shielded from the anode 12. In the construction illustratedin FIGS. 1 and 2, the basket-like filament support 45 serves as agradient shield for the cathode filament 48. The support acts as a lowmu grid surrounding the cathode filament 48, the larger the number ofU-shaped rods 46, the greater the shielding effect of the support 45 onthe filament 48. The ends of the rods 46 are formed inwardly toterminate within tubular conductor 26, as mentioned, and the upper endof the cathode filament 48 is carefully welded to the underside of theconnecting portion 64 (FIG. 2) of the 'U-shaped rods 46 so as not toextend outside the confines of the support structure 45. By these means,any sharp edges at the ends of the filament wire or U-shaped rods 46 arecarefully shielded and prevented from being the cause of localizedexcessively high gradients.

Some idea of the advantages provided by this invention may be realizedby a comparison of a tube made according to this invention with acommercially available and extensively used rectifier tube having acoaxial tubular electrode structure. Tube type 3A3 is a glass octal tubetype having an envelope diameter of 1.125 inches, an anode innerdiameter of .563 inch, a cathode diameter of .025 inch, and a cathodesupport structure comprising a single U-shaped rod, the planar distancebetween the outside surfaces of the legs of the U (that is, the outerdiameter of the support) being 0.250 inch.

For a value of inverse voltage of 50 kilovolts, analysis of the 3A3structure reveals that the maximum potential gradient at the surface ofthe anode is about eighty-six thousand volts per centimeter, and abouttwo-hundred and twenty-five thousand volts per centimeter at the surfaceof the filament. For a tube made according to this invention having anenvelope diameter of only about .790 inch, an anode inner diameter ofabout .780 inch, and a filament support 45 outer diameter of about 0.080inch, the maximum anode potential gradient is only twenty-two thousandvolts per centimeter, while the cathode potential gradient is abouttwo-hundred and twenty thousand volts per centimeter. The reason for thelarge differences in anode potential gradients between the two tubes isapparent upon examination of the graphs of FIG. 5. The cathode-anodediameter ratios for the 3A3 and the tube of this invention are 0.44 and0.1, respectively, and from curve 2 of FIG. 5 it is to be expected thatthe anode surface gradient for the 3A3 would be much greater than theanode surface gradient for the tube of this invention.

The fact that the cathode potential gradients are about the same isexplained as follows: Because of the relatively small shielding effectof the single rod filament support upon the filament of the 3A3, thepotential distribution about the surface of the 3A3 filament isnonuniform. That is, because of the low mu of the filament support andits relatively close spacing to the anode, the shielding effect of thesupport on the filament varies materially from a point on the filamentsurface in the plane of the sides of the U-shaped support to a point onthe filament surface in a plane perpendicular to the first plane. In thefirst plane, the value of cathode to anode ratio is 0.44, as mentioned,which results in a low cathode surface potential gradient. In the planeperpendicular to the first plane, however, the shielding effect of thesupport on the filament is so slight that the diameter ratio cannotproperly be considered as 0.44.. In this plane, the diameter ratio isnearer a value of 0.05 which is the value computed on the basis of thediameter of the cathode filament itself with respect to the anode. Fromcurve 1 of FIG. 5, it is apparent that the cathode surface gradient forsuch a low diameter ratio is very high. Thus, although parts of thefilament of the 3A3 have relatively low surface gradients, other partsthereof have relatively large gradients, the larger gradients, as known,being the limiting factors determining the utility of the tube. Afurther advantage of this invention is the ease with which the tube maybe assembled. As shown in FIG. 7, a jig 70 for fabricating the electrontube shown in FIG. 1 includes a number of jigging surfaces or elements71 therein adapted for receiving certain ones of the tube components inproperly spaced relationship. In the assembly and fabrication of theelectron tube, the jig 70 is oriented with its open end up and theconductor rod 31, tubular conductor 26, and ceramic insulator 13 areloaded into contact with the jigging elements 71 as shown. The tubularportion 16 is then loaded on top of ceramic insulator 13, and flanges 29and 34 are deposited in the order named onto the ends of tubularconductor 26 and conductor rod 31, respectively. The ends of tubularportions 30 and 33 of flanges 29 and 34, respectively, have inwardlyturned lip portions 66 for providing positioning and balancing means forthe flanges 29 and 34 on the ends of conductor 26 and rod 31. ClosureWafer 18 is then fitted to tubular portion 16 within flange 19 thereon,and lead-ins 36 are dropped through bores extending through wafer 18 toengage with and rest upon flange 34. Prior to such assembly, the ceramicwafer 18 has been provided with a metallic coating on its outerperiphery which engages flange 19, and the walls of the bores likewise.The lead-ins 36, flanges 29 and 34, and tubular portion 16 have alsobeen suitably coated with a brazing material.

The loaded jig 70 is then inserted into a furnace and heated in areducing atmosphere at a temperature sufiicient to melt the brazingmetal coatings. Upon cooling, the parts referred to are uniformly andcompletely brazed together to form a unitary mount structure.

Following the brazing operation, the mount structure is removed from thejig 70, and an insulating washer 40 is inserted into tubular conductor26 and fitted onto'the conductor rod 31 therein. Also, the filamentsupport structure 45 and the cathode filament 48 are welded .to the ends43 and 38 of tubular conductor 26 and conductor rod 31, respectively,one end of the filament 48 having been previously welded to the supportstructure 45.

For completing the tube assembly, an exhaust jig 80 (FIG. 8) isemployed. Jig 80 comprises a cup portion 82 adapted for receiving theanode 12 therein, and a tubular jig insert 84 adapted for receiving theceramic insulator 13. Cup portion 82 and insert 84 are dimensioned toreceive their receptive tube parts in relatively snug fit.

In the final assembly of the tube, the anode 12 is first dropped intocup portion 82. A ring of preformed brazing material 86 is then placedon the end of the anode 12. Thereafter, a flange portion 87 of insert 84is engaged with a flange portion 88 of the cup portion 84, and the mountstructure then inserted into insert 84. Ceramic insulator 13 isautomatically aligned with the end of anode 12 as shown whereby exactcentering of the anode 12 with respect to the mount structure and hencethe cathode assembly is achieved. Exact centering and concentricity ofthe anode and cathode structures is very important for avoidingnon-uniform electrostatic forces about the surface of the cathodeassembly. Such non-uniform stress, as known, tend to cause distortion 8of the fragile filament 48 and eventual destruction of the electrontube.

The loaded exhaust jig is then subjected to a final heating in vacuum.This final processing step serves to evacuate the tube, activate thecathode filament 48, and solder the anode 12 to the ceramic insulator13. The temperature employed in this final step is substantially belowthe previous brazing temperature. Accordingly, the previously madebrazes are not affected. Although not described, the tube constructionsshown in FIGS. 3 and 4 may be fabricated in substantially the samemanner.

What is claimed is:

1. An electron discharge device comprising an envelope including aheader assembly, a tubular member, and an anode, said tubular memberhaving a predetermined inner diameter, an elongated conduct-or extendingthrough said tubular member and into said anode, a portion of the lengthof said conductor and substantially the entire length of said tubularmember defining an unoccupied space therebetween, and a cathode assemblymounted on the end of said conductor within said anode, the maximumradial dimension of said portion of said conductor being less than 0.2of said predetermined diameter.

2. An electron discharge device comprising an envelope including instacked end to end relationship, a cup-shaped header assembly, a tubularmember, and a cup-shaped anode, said tubular member being intermediateand separating said header assembly and said anode, and said tubularmember having a predetermined diameter inner, an elongated conductorsupported at one end thereof within said header assembly, said conductorextending axially of said envelope from said header assembly throughsaid tubular member and into said anode, a portion of the length of saidconductor and substantially the entire length of said tubular memberdefining an unoccupied space therebetween, and a cathode assemblymounted on the end of said conductor Within said anode, the maximumradial dimension of said portion of said conductor being less than 0.2of said predetermined diameter.

3. An electron discharge device comprising an envelope including atubular member, and an anode, said anode having a tubular portion of afirst predetermined diameter, and said tubular member having a secondpredetermined diameter, an elongated conductor extending through saidtubular member and into said anode, and a cathode assembly mounted onthe end of said conductor within said anode, the radial dimensions ofsaid cathode assembly being less than 0.2 and more than 0.09 of saidfirst diameter, and the maximum radial dimension of said conductor beingless than 0.2 of said second diameter.

4. An electron discharge device comprising an envelope including aheader assembly, a tubular member, and an anode, said anode having atubular portion of a first predetermined diameter, and said tubularmember having a second predetermined diameter, an elongated conductorsupported at one end thereof within said header assembly, sa d conductorextending from said header assembly into said anode, and a cathodeassembly mounted on the end of said conductor within said anode, theradial dimensions of said cathode assembly being less than 0.2 and morethan 0.09 of said first diameter, and the maximum radial dimension ofsaid conductor being less than 0.2 of said sec- 0nd diameter.

5. An electron discharge device comprising an envelope including instacked end to end relationship, a cupshaped header assembly, a tubularmember, and a cupshaped anode, said tubular member being intermediateand separating said header assembly and said anode, said anode having atubular portion of a first predetermined diameter, and said tubularmember having a second predetermined diameter, an elongated conductorsupported at one end thereof within said header assembly, said conductorextending axially of said envelope from said header assembly throughsaid tubular member and into said an- 9 ode, and a cathode assemblymounted on the end of said conductor within said anode, the radialdimensions of said cathode assembly being within 0.09 and 0.2 of saidfirst diameter and the maximum radial dimension of said conductor beingless than 0.2 of said second diameter.

6. An electron discharge device comprising an envelope including instacked end to end relation, a cup-shaped header assembly, a tubularceramic member and a cupshaped anode, said ceramic member beingintermediate and separating said header assembly and said anode, saidanode having a tubular portion of a first predetermined diameter, saidtubular ceramic member having a second predetermined diameter, and saidheader assembly comprising a conductive tubular portion closed at an endremote from said ceramic member by a ceramic closure member, anelongated tubular conductor supported at one end thereof within saidheader assembly and secured to said tubular portion, said tubularconductor extending axially of said envelope from said header assemblythrough said tubular ceramic member and into said anode, and a cathodeassembly mounted on the end of said tubular conductor within said anode,the radial dimensions of said cathode assembly being within 0.09 and 0.2of said first diameter and the maximum radial dimension of said tubularconductor being less than 0.2 of said second diameter.

7. An electron discharge device comprising in stacked end to endrelation, a cup-shaped header asembly, a tubular ceramic member, and acup-shaped anode, said ceramic member being intermediate and separatingsaid header assembly and said anode, said stacked elements providing aclosed envelope, the inner peripheral lip of the end of said ceramicmember in engagement with said anode being beveled, said anode having atubular portion of a first predetermined diameter, said ceramic memberhaving a second predetermined diameter, and said header assemblycomprising a conductive tubular portion closed at an end remote fromsaid ceramic member by a ceramic closure member, an elongated tubularconductor supported at one end thereof Within said header assembly andsecured to said tubular portion, said tubular conductor extendingaxially of said envelope from said header assembly through said ceramicmember and into said anode, a conductor rod extending through andoutwardly of said tubular conductor, said rod being supported at one endthereof by a lead-in extending through said ceramic closure member, andan electron emitting element supported at one end thereof on the end ofsaid tubular conductor within said anode and having its other endsupported by said conductor rod, radial dimensions of said electronemitting element being Within 0.09 and 0.2 of said first dimension, andthe maximum radial dimension of said tubular conductor being less than0.2 of said second dimension, said tubular portion and said lead-inserving as thermals for said electron emitting element.

8. A high voltage rectifier electron tube comprising a shallowcup-shaped header assembly, said header assembly including a conductive,open-ended tubular member having a flange at the periphery of one endthereof, a ceramic closure member sealed within said tubular member atsaid flange, an elongated ceramic tubular envelope portion of a firstpredetermined diameter having one end sealed to the other end of saidtubular member, an elongated cup-shaped anode sealed to the opposite endof said ceramic tubular portion and providing with said ceramic tubularportion and said header assembly an envelope, said anode having atubular portion of a second predetermined diameter, an elongatedconducting tubular member secured at one end thereof to the tubularportion of said header assembly and extending axially of said ceramictubular portion and into said anode, said conducting tubular memberhaving an outer diameter less than 0.2 of said first predetermineddiameter, a U-shaped supporting element mounted on the other end of saidconducting tubular element within said anode, the radial di- 10 mensionsof said U-shaped supporting element being within 0.09 and 0.2 of saidsecond predetermined diameter, a conductor rod extending upwardlythrough and out wardly of each end of said conducting tubular member,said rod being secured at its lower end to a lead-in extending throughsaid ceramic closure member, and a cathode filament secured at one endthereof to a portion of said -shaped supporting element and having itsother end connected to said rod, said lead-in and said tubular portionof said header assembly serving as the terminals for said cathodefilament.

9. A high voltage rectifier electron tube having an envelope comprisinga tubular conductive member, an elongated tubular insulating membersealed at one end to one end of the tubular conductive member, aninverted cup-shaped anode electrode sealed to the other end of saidelongated tubular insulating member, an insulating closure member'sealedto the end of said conductive tubular member at its opposite end fromsaid elongated tubular insulating member, a first transverse flangesecured at its periphery to the interior of said tubular conductivemember, an elongated tubular conducting member secured at one end tosaid flange centrally thereof and supported thereby, a conductorextending through said elongated tubular conducting member, a secondflange positioned between the first transverse flange and saidinsulating closure member, said conductor secured to and supported bysaid second flange, a lead extending through and sealed in said closuremember, one end of said lead being secured to said second flange, and acathode assembly supported at the end of said elongated tubularconducting member Within said anode, said conductor and said elongatedtubular conducting member providing electrical connection with saidcathode assembly.

10. A high voltage rectifier electron tube comprising a shallowcup-shaped header member, said header member including a conductive,open-ended tubular member having a flange at the periphery of one endthereof, a ceramic closure member sealed within said tubular member atsaid flange, an elongated ceramic tubular envelope portion having oneend sealed to the other end of said tubular member, an elongatedcup-shaped anode sealed to the opposite end of said ceramic tubularportion and providing with said ceramic tubular portion and said headeran envelope, an elongated conducting tubular member secured at one endthereof to the tubular portion of said header and extending axially ofsaid ceramic tubular portion and into said anode, a U-shaped supportingelement mounted on the other end of said conducting tubular .elementWithin said anode, a conductor rod extending upwardly through andoutwardly of each end of said conducting tubular member, said rod beingsecured at its lower end to a lead-in extending through said ceramicclosure member, and a cathode filament supported at one end thereof to aportion of said U-shaped supporting element and having its other endsecured to said rod, said lead-in and said tubular portion of saidheader serving as the terminals for said cathode filament.

11. A high voltage rectifier electron tube comprising a shallowcup-shaped header member, said header member including a conductive,open-ended tubular member having a flange at the periphery of one endthereof, a ceramic closure member sealed Within said tubular member atsaid flange, an elongated ceramic tubular envelope portion having oneend sealed to the other end of said tubular member, an elongatedcup-shaped anode sealed to the opposite end of said ceramic tubularportion and providing with said ceramic tubular portion and said headeran envelope, an elongated conducting tubular member secured at one endthereof to the tubular portion of said header and extending axially ofsaid ceramic tubular portion and into said anode, a supporting elementmounted at the other end of said conducting tubular element within saidanode, said supporting element comprising a plurality of U-shape rodsarranged to form a basketlike structure, a conductor rod extendingupwardly through and outwardly of each end of said conducting tubularmember, said rod being secured at its lower end to a lead-in extendingthrough said ceramic closure member, and a cathode filament supported atone end thereof to a portion of said supporting element remote from saidtubular conducting member and having its other end secured to said rod,said lead-in and said tubular portion of said header serving as theterminals for said cathode filament.

12. A high voltage rectifier electron tube comprising a shallowcup-shaped header member, said header member including a conductive,open-ended tubular member hav ing a flange at the periphery of one endthereof, said flange extending parallel to and in the same direction assaid tubular member, a ceramic closure member sealed within said tubularmember at said flange, an elongated ceramic tubular envelope portion ofa first predetermined diameter having one end sealed to the other end ofsaid tubular member, an elongated cup-shaped anode sealed to theopposite end of said ceramic tubular portion and providing with saidceramic tubular portion and said header an envelope, said anode having atubular portion of a second predetermined diameters, an elongatedconducting tubular member secured at one end thereof to the tubularportion of said header and extending axially of said ceramic tubularportion and into said anode, said conducting tubular member having anouter diameter less the 0.2 of said first predetermined diameter, anindirectly heated cathode mounted at the other end of said conductingtubular element within said anode, the largest radial dimension of saidcathode being within 0.09 and 0.2 of said second predetermined diameter,a conductor rod extending upwardly through and, outwardly of each end ofsaid conducting tubular member, said rod being secured Cir at its lowerend to a lead-in extending through said ceramic closure member, and saidrod being insulatingly supported adjacent its upper end within saidconducting tubular member, and a heating element included within saidcathode, one end of said heating element being secured to said cathode,and the other end thereof being secured to said rod, said tubularportion of said header serving as terminals for said cathode and saidheating element, and said lead-in serving as the other terminal for saidheating element.

13. An electron discharge device comprising an envelope including aheader assembly, a tubular member having a predetermined inner diameter,and an anode, an elongated conductor extending through said tubularmember, a portion of the length of said conductor and substantially theentire length of said tubular member defining and unoccupied spacetherebetween, and a cathode assembly mounted on the end of saidconductor within said anode, the maximum radial dimension of saidportion of said conductor being less than 0.2 of said predetermineddiameter.

References Cited by the Examiner UNITED STATES PATENTS 2,719,185 9/55Sorg et al 3l3250 X 2,812,466 11/57 Murdock 313-3 17 FOREIGN PATENTS815,655 5/56 Great Britain.

DAVID J. GALVIN, Primary Examiner.

RALPH G. NILSON, ARTHUR GAUSS, JAMES D.

KALLAM, Examiners.

1. AN ELECTRON DISCHARGE DEVICE COMPRISING AN ENVELOPE INCLUDING AHEADER ASSEMBLY, ATUBULAR MEMBER, AND AN ANODE, SAID TUBULAR MEMBERHAVING A PREDETERMINED INNER DIAMETER, ADN ELONGATED CONDUCTOR EXTENDINGTHROUGH SAID TUBULAR MEMBER AND INTO SAID ANODE, A PORTION OF THE LENGTHOF SAID CONDUCTOR AND SUBSTANTIALLY THE ENTIRE LENGTH OF SAID TUBULARMEMBER DEFINING AN UNOCCUPIED SPACE THEREBETWEEN, AND A CATHODE ASSEMBLYMOUNTED ON